well I understand the meaning of static (you don't need to instantiate the object manually to reference it, it's already instantiated). My question was wronngly worded. I meant to ask why do I need to use static (why doesn't it work without static, i.e. it's null object w/o static). In a SFSB this is not the case.

You already indicated that it's not advisable to use a Seam POJO as an interceptor so perhaps this has something to do with it...